Loads of threads on what to look for. I'm not even going to tell you to search, because you could probably just scroll down the main "discussion" forum and find 5

The most important bit of advice though IMO: spend proper money on a good example and it'll be a fantastic car you'll love. Buy a cheap/abused one and everything you've heard about French (un)reliability will come true.
Insurance is all about statistics (i.e. how many 172s have been written off or where you live) and YOU (convictions, crashes, education/job). Since there is only one of you, no-one can give you an exact answer. If you have similar traits to myself, you'll find a 182 is actually CHEAPER. For ME the insurance company figure I'm more likely to take care of 3 or 4k 182 than a 2k 172. That and far more 172s will have been involved in convictions, deaths by dangerous driving and write offs because they are much cheaper to buy = 172s are a higher risk.
P.S. Before the CS Police arrive this is a "clio sport" in all it's 1.2L glory...
And this is a "Clio Renaultsport" (or 172/182/RS Clio/Ph2 RS etc as the enthusiasts like to call them) in all of it's 2.0L hot-hatch glory: